The present disclosure relates to a communication apparatus such as a power line communication modem used for power line communication in which data communication is performed using an indoor power line and its communication method.
Power line communication modems used in this type of field use several communication procedures. When communication procedures are different, they cannot coexist, for example, in one and the same house. The use of modems using different communication procedures in one and the same house is expected in future, and therefore formulation of a coexistence procedure has been awaited.
In FIG. 3 of page 65 of “High-speed Power Line Communication (issued by Nikkei Business Publications, Inc., 20 Jul. 2006),” an example in which a plurality of TDMA slots are each used by different systems, a “system 1”, a “system 2”, . . . , is shown.
One TDM unit in a power line communication procedure under study is constituted by a fixed-length time slot for best-effort type transmission and, for example, four fixed-length time slots for bandwidth reservation type transmission. The power line communication procedure includes a TDMA procedure and a CSMA procedure, and the former is assigned to the bandwidth reservation type time slot, whereas the latter is assigned to the best-effort type time slot.
When the TDMA procedure is adopted, a Beacon signal is transmitted at regular intervals and the interval is time-divided to perform data transmission. One system constituted by a Master and a plurality of slaves is assigned to the bandwidth reservation type time slot. One system uses one or a plurality of time slots according to a necessary transmission speed.
Incidentally, when data to be transmitted does not exist in a system using the TDMA procedure, only the Beacon signal is repeatedly transmitted. The Beacon signal is a transmission indispensable to the system using the TDMA procedure and therefore cannot be stopped. Hence, even when there is no data to be transmitted, the bandwidth reservation type slot continues being used to transmit the Beacon signal. Accordingly, in the case of the above example, up to four systems can coexist, and more than four systems cannot coexist.
In view of the above circumstances, it is desirable to provide a communication apparatus and a communication method capable of relaxing the numerical restriction of systems which can coexist.